Motor control



May 21, 1963 J. W. HAMMANN MOTOR CONTROL Filed April 16, 1959 FIGZ United @rates snsaaa/ MOTR CONTROL John W. Hammam, S55 Carter Ave., St. Louis l5, M0. Filed Apr. 16, i959, Ser. No. 306,833 4 claims. (ci. aia-isa) Tne present invention relates generally to motor controls and more particularly to a control for an alternating current motor employing oscillator principles and energiZed by a direct current source.

Various means have been devised in the past for utilizing electronic oscillator principles to control the operation of a motor. The known devices, however, unlike the present device have not been self starting without special devices or cumbersome equipment, have not used the motor winding to load an oscillator, have not employed push-pull oscillator oper-ation using semi-conductors, and have not employed Yoscillator tuning means to adjust the motor speed. For these and other reasons the present device represents an important advance in the motor art,

lt is therefore a major object of this invention to provide an alternating current motor operable from a direct current source.

Another object is to provide relatively simple means of operating a known single or polyphase alternating current motor from a -battery or other direct current source.

Another important object is to provide a motor, the windings -of which are connected as part of a tuned circuit.

Another object is to eliminate the need for commutators and brushes on motors operated from direct current.

Another object is to provide a motor, the windings of which are connected as parts of tuned circuits.

Another object is to control the operation and speed of a motor by a tunable electronic circuit.

Another object is to use semi-conductor or other electronic devices in the control circuit of a motor.

Another object is to use frequency tuning principles to control the speed of a motor.

Another object is to provide relatively more precise means for adjusting the speed of a motor, which means are capable of adjusting the Vspeed to any value within the range thereof.

Another object is to minimize the number of wear parts in a motor.

Another object is to provide a relatively inexpensive motor construction which can be built in unusually small sizes and ratings with minimum input power requirement, as well as in larger ysizes and ratings.

Another object is to provide a motor unusually well Y suited for use in portable equipment.

Still another `object is to provide a motor which can be easily controlled and adjusted to operate in synchronisin with other motors.

These and other objects and advantages of the present invention will become apparent after considering the following detailed drawing.

ln the drawing:

FlG. l is a schematic wiring diagram of a circuit for a motor constructed according to the present invention.

FIG. 2 is a block diagram of a two-phase motor, the windings of which are connected in control circuits constructed according to the present invention, and

FIG. 3 is a block diagram similar to FlG. 2, showing application of the present invention to a three-phase motor.

Referring to FIG. l in detail, the number llt) refers generally to a motor circuit constructed according to the present invention. The motor circuit lll has a motor winding 12 connected therein which is divided into portions 12a and 12b, with an intermediate connection 14 ice between said portions and with end connections 16 and 13. The intermediate connection 11i is connected to the minus terminal of a battery Zit by lead 22 and the plus terminal of the battery 20 is connected to a terminal 24 by lead 26. The terminal 24 is connected by leads 36 and 38 to emitter elements 2S and 30 on semi-conductor elements, or transistors 32 and 34, respectively. The transistor 32 also has a collector element 40 which is connected by leads 42 and 44 to the motor end connection lo; and the transistor 34 has a collector element 46 connected by leads 48 and Sn to the opposite end connection li on the motor winding 12.

The collector element iii on the transistor 32 is also connected via leads 42 and 52 to one side of a capacitor 54, the other side of which is connected by lead 56 to a resistor element 58, and by a parallel lead 60 to one side of an adjustable capacitor 62.

The opposite sides of the capacitor 62 and the opposite side of the resistor 5S are connected via leads 64 and 66 respectively to one side of another capacitor 70. The other side of the capacitor 7i) is connected by lead 72 to the junction of leads 48 and Sti.

The terminal 24 which is connected to the plus side of the battery 2li is also connected by lead 74 to an intermediate terminal '76 on the resistor 58.

The transistor 32 also has a base element 7S which is connected by a lead @il to another intermediate terminal 82 on the resistor Sii, and the terminal S2 .is positioned on the `resistor 58 between the terminal 76 and the lead 66 in order to provide proper circuit feed back as will be explained hereinafter. Similarly the transistor 34 has a base element 34 which is connected by lead 86 to a terminal 88 on the resistor 58, which terminal S8 is between the terminal 76 and the lead 56. The circuit that has been described is ythat of a push-pull amplifier which oscillates at `a frequency which is dependent upon the particular elements chosen and, to :Some extent, yon the loading of the motor.

It should be noted that the resistor Sie can be a single resistor element with suitable intermediate connector positions or it can be four separate resistors such as the resistor portions 58a, 58h, SSC and 58d which together comprise the resistor SS.

It is now apparent that the portions 12a and Zb of the motor winding 12 are connected respectively and in series with the battery 2Q (or any other `suitable direct current source) across the transistors 32. and 34 (from emitter to collector elements), and furthermore are connected in parallel with circuits consisting of tbe associated capacitor 54- (or 76) and the associated portions of the resistor 58.

The base elements 78 and S4 on the transistors 32 and 34 are connected to intermediate location on the portions of the resistor 58 associated with the circuit of the opposite transistor. This is done to provide positive feed back into the circuits to make the circuits oscillate.

rhe variable capacitor 62 is connected across the resistor S8 and affects the operation of both oscillator circuits, and also serves as a bypass for the resistor 5S and as convenient imeans for varying the oscillation frequency and hence the speed of the motor. This is apparent because the capacitor 62 is connected in series with the resistor portions 53e and 59rd across the resistor portions 58a and SSI), and .similarly is connected in series with the portions 53a and 581; across the portions 58e and 58d. The speed of the motor lis also aected by the magnitudes lof the resistance portions 5&1, 58h, 53C and 58d.

The circuit associated with both transistors 32 and 34 are oscillator circuits and the two separate circuits are constructed and designed to operate in push-pull. The

frequency of oscillation of the circuits is determined primarily by the inductance of the motor winding in each circuit and by the capacitance connected in parallel therewith, the combination thereof operating as a resonant inductive-capacitive (L-C) or tank circuit.

The by-pass capacitor 62, the resistor 5S land the semiconductors 32 and 3d also affect the oscillating frequency because they form part of the oscillator circuits. Furthermore, the capacitor 62 permits oscillation at lower frequencies than would otherwise be possible and also serves as a by-pass across the resistor 53- as previously stated.

The taps 82 and SS on resistor 5S are for the purpose of impedance matching and for controlling the feed back currents. The position of the taps also affects the frequency of oscillation.

The feed back circuits are provided to sustain the oscillations by feeding back some positive amount of energy of the collector-emitter circuit to the base elements 78 and 84 of the other oscillator circuit. To sustain oscillation the energy fed back rnust be positive at the right instants as is well known.

FIG. 2 shows a typical two-phase motor lli-fil` having windings 102 and 1M both of which are connected to control circuits il@ as described herein. The two control circuits 1.6* are also shown connected to coupling means 1% which provide substantially 90 degrees phase displacement therebetween.

FIG. 3 shows adaptation of the present control circuit l@ to a three-phase motor 2%. ln this case also a separate control circuit it? is connected to each motor winding 262, 204 and 266 and two coupling circuits 238 are provided between the control circuits as shown. Obviously the present control circuit could also be used with other poly-phase -rnotor constructions as well.

While the present device has been illustrated in conection with la particular oscillator circuit employing transistors, it -is anticipated that other known types of oscillator circuits could also be constructed using other types of semi-conductor devices, vacuum tubes or thyratrons without departing from the spirit and scope thereof. If the device is constructed using transistors, as shown, it can be made in relatively small sizes capable of occupying minimum space, or it can be made in larger sizes using semi-conductors capable of Ihandling substantial currents. It is also contemplated to employ the present device in conjunction with either the stator or the rotor windings of a motor.

Still further, it is also anticipated that the present device be constructed without using a variable capacitor such as the capacitor 62, in which case it would probably be desirable to make one or both of the capacitors 54 and 76 variable.

Thus it is apparent that there has been shown and described a control circuit for a motor comprising a pushpull oscillator network having resonant circuits formed in part by the windings of a motor itself and energized l by a direct current source; which control fulfills all of the objects and advantages sought therefor.

Gbviously, many changes, alterations, modications and variations of the present device can be made by those skilled in the art without departing from the spirit and scope of the invention. All such changes, alterations, modifications and variations which do not depart from the spirit and scope of the invention are deemed covered by the invention which is limited only by the claims which follow.

What is claimed is:

l. A control circuit network for a two phase motor having a pair of phase windings therein comprising an oscillator circuit associated with both of the motor windings, each of said oscillator circuits having a pair of tunable circuits formed in part by a different portion of the 'motor winding associated therewith, means connecting the tunable circuits in each oscillator circuit for pushpull operation, a source of energy connected to said oscillator circuits, and means in each of said oscillator circuits for changing the frequency of oscillation of the associated tunable circuits.

2. The control circuit dened in claim 1 wherein coupling means are connected between said oscillator circuits to provide phase displacement between the electrical energy in said circuits.

3. A control circuit network for a polyphase motor having a plurality of phase windings comprising an oscillator circuit associated with each of the motor windings, each of said oscillator circuits having a pair of tunable circuits formed in part by different portions of the associated motor winding, means connected said tunable circuits for push-pull operation, a source of direct current energy connected to said oscillator circuits, and coupling means connected between at least two of said oscillator circuits to provide phase displacement between the electrical energy in said circuits.

4. A control circuit network for a polyphase motor having a winding associated with each phase comprising an oscillator circuit associated with each of the motor windings, each of said oscillator circuits having a pair of tunable circuits yformed in part by different portions of the associated motor winding, means connecting said tunable circuits associated with each winding for pushpull operation, coupling means connected between at least two of said oscillator circuits to provide positive feedback from one of said circuits to the other to cause said circuits to oscillate, and a direct current energy source connected to said network.

References Cited in the tile of this patent UNITED STATES PATENTS 2,796,571 Dunn lune 18, 1957 2,810,843 Granqvist Oct. 22, 1957 2,814,769 Williams Nov. 26, 1957 

1. A CONTROL CIRCUIT NETWORK FOR A TWO PHASE MOTOR HAVING A PAIR OF PHASE WINDINGS THEREIN COMPRISING AN OCSILLATOR CIRCUIT ASSOCIATED WITH BOTH OF THE MOTOR WINDINGS, EACH OF SAID OSCILLATOR CIRCUITS HAVING A PAIR OF TUNABLE CIRCUITS FORMED IN PART BY A DIFFERENT PORTION OF THE MOTOR WINDING ASSOCIATED THEREWITH,MEANS CONNECTING THE TUNABLE CIRCUITS IN EACH OSCILLATOR CIRCUIT FOR PUSHPULL OPERATION, A SOURCE OF ENERGY CONNECTED TO SAID OSCILLATOR CIRCUITS, AND MEANS IN EACH OF SAID OSCILLATOR CIRCUITS FOR CHANGING THE FREQUENCY OF OSCILLATION OF THE ASSOCIATED TUNABLE CIRCUITS. 